Relative positioning for vehicles using gps enhanced with bluetooth range finding

ABSTRACT

A relative vehicle positioning system for a vehicle includes a GPS antenna adapted to receive satellite signals generated in response to relative vehicle positioning and generate therefrom a GPS signal. A Bluetooth radio is adapted to exchange bearing information with a second vehicle and generate therefrom a PVT signal. A GPS unit including a controller is adapted to receive the GPS signal and the PVT signal, the GPS unit is further adapted to generate therefrom a GPS-Bluetooth relative position signal.

TECHNICAL FIELD

[0001] The present invention relates generally to vehicle communicationsystems, and more particularly to a method and apparatus forcommunicating between multiple vehicles in close proximity to eachother.

BACKGROUND OF THE INVENTION

[0002] Collision countermeasure and warning systems are becoming morewidely used. These systems detect objects or vehicles within closeproximity of a vehicle and perform safety operations to prevent orminimize the likelihood of a collision and any resulting injury to anoccupant.

[0003] Through the development of collision countermeasure and warningsystems, vehicle-to-vehicle communications have been suggested forincreased vehicle awareness of other vehicles or potentially hazardousconditions that may exist within close proximity to the vehicle.

[0004] Vehicle-to-vehicle communication for safety purposes requiresseveral distinct types of data communication. It would be beneficial ifa vehicle was aware of other vehicles that may be approaching frommultiple directions and at various velocities. It would also bebeneficial if a vehicle was aware of various traffic conditions, such asa slow moving congested traffic situation versus a clear faster movingsituation when a first vehicle may pass a second vehicle. Thus, it wouldbe advantageous if a vehicle in motion was able to discover andcommunicate with other vehicles that are traveling in a concurrentmanner, including vehicles approaching from a forward, rearward, orlateral direction of a first vehicle.

[0005] Traditional vehicle communication systems have a vehicle timedelay discovery problem. The greater the relative speed of the vehicles,and the shorter the range of the Bluetooth devices, the more significantthe synchronization time delay.

[0006] Traditional vehicle communication systems discover vehicles inclose proximity under slow moving traffic conditions. Generally, duringa slow moving traffic condition, vehicles tend to remain in a vehiclerange for a longer period of time, allowing the vehicle to discover theother vehicles without any timing issues.

[0007] The synchronization time delay is quite evident when vehiclesapproach head-on because the relative speed is large and the possibilityexists that they will not synchronize before they pass. It is also quiteevident when the vehicles move lateral to each other because objects offthe road may interfere with the signal.

[0008] The lateral approaching vehicle situation introduces anadditional problem with existing vehicle communication systems. Objectsbetween the first vehicle and the approaching vehicle may blockcommunication signals and make detecting laterally approaching vehiclesdifficult. Thus, network communication is crucial to provide advancedwarning of objects or potential hazards to vehicles within the network.

[0009] Ad hoc wireless mobile networks are commonly used because oftheir associated desirable benefits for vehicle-to-vehicle datacommunication including: lack of reliance on third partyinfrastructures, ability to adapt to local conditions readily, abilityto allocate resources on a local level, and absence of single points offailure. Also, commodity implementations of ad hoc networking hardwareare readily available and well proven. However, ad hoc wireless mobilenetworks have disadvantages associated with routing of communicationsignals.

[0010] Many pre-crash and crash avoidance technologies require knowledgeof a vehicle location and velocity with respect to locations andvelocities of other nearby vehicles. Global Positioning Systems (GPS)provide this type of information, but frequently without the necessaryaccuracy.

[0011] Current GPS require twenty-four operational satellites toguarantee that there are at least four above the horizon for any pointon Earth at any given time.

[0012] Currently, GPS devices are connected to a computer in a vehicleequipped with a two-way digital radio for communicating with thevehicles around it. Position, Velocity and Time (PVT) data is computedin the GPS and passed to the computer, typically using the NationalMarine Electronics Association (NMEA) standards. The computed PVT datais exchanged between vehicles using two-way digital radios, wirelessmodems, or network devices such as those conforming to the IEEE 802.11,802.1 la, or 802.1 lb specifications. The known position and velocityvectors are subtracted to give the relative velocity vectors.

[0013] The errors attributed to the GPS receivers have not beeneliminated in this way, however, and these errors are multiplied in theposition calculation because they are quite sensitive to the geometricrelationship between the satellites that are being used. Further, eachvehicle GPS must be able to receive signals from at least foursatellites simultaneously for the method to work. Buildings, overpassesand foliage may limit the number of satellite “visible” to thereceivers. These factors all reduce the effectiveness of this approachas a solution to vehicle positioning for the purposes of vehicle safety,navigation and Telematics.

[0014] It would therefore be desirable to develop a wireless mobilecommunication network for vehicle-to-vehicle communication that isfeasible to implement for various approaching vehicle situations, thatovercomes the above mentioned timing and accuracy issues.

SUMMARY OF THE INVENTION

[0015] The present invention provides a method and apparatus forcommunicating between multiple vehicles in close proximity to eachother. In accordance with one aspect of the present invention, arelative vehicle positioning system for a first vehicle includes a GPSantenna adapted to receive satellite signals generated in response torelative vehicle positioning and generate therefrom a GPS signal. Afirst Bluetooth radio is adapted to exchange bearing information with asecond vehicle and generate therefrom a PVT signal. A GPS unit includinga controller is adapted to receive the GPS signal and the PVT signal,and generate therefrom, a GPS-Bluetooth relative position signal.

[0016] In accordance with another aspect of the present invention, amethod of communicating between vehicles having GPS-Bluetooth devices isprovided. The method includes receiving timing and vehicle data,generating a GPS signal, computing range and velocity through Dopplershift, sharing information between the Bluetooth devices, andsynchronizing the GPS-Bluetooth devices.

[0017] The GPS-Bluetooth system in the present invention improves GPSfor vehicle navigation and other purposes as well as vehicle safety andpre-crash sensing.

[0018] Furthermore, the present invention utilizes multiple vehicletechnologies that are widely available to minimize additional costs to avehicle system.

[0019] Other advantages and features of the present invention willbecome apparent when viewed in light of the detailed description of thepreferred embodiment when taken in conjunction with the attacheddrawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a relative positioning system in accordance with oneembodiment of the present invention;

[0021]FIG. 2A is a vehicle merging diagram in accordance with oneapplication of the present invention;

[0022]FIG. 2B is a vehicle intersection diagram in accordance withanother application of the present invention;

[0023]FIG. 2C is a vehicle passing diagram in accordance with anotherapplication of the present invention;

[0024]FIG. 2D is a vehicle following another vehicle diagram inaccordance with another application of the present invention;

[0025]FIG. 3 is a block diagrammatic view of an inter-vehiclecommunication system in accordance with another embodiment of thepresent invention;

[0026]FIG. 4 is a relative positioning system in accordance with anotherembodiment of the present invention;

[0027]FIG. 5 is a logic flow diagram of a method for relative vehiclepositioning in accordance with another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] In each of the following figures, the same reference numerals areused to refer to the same components. While the present invention isdescribed with respect to a method and apparatus for communicatingbetween multiple vehicles in close proximity to each other, the presentinvention may be adapted for use in various systems including:automotive vehicle systems, control systems, communication systems, orother systems that may utilize GPS or the like.

[0029] In the following description, various operating parameters andcomponents are described for one constructed embodiment. These specificparameters and components are included as examples and are not meant tobe limiting.

[0030] Referring to FIG. 1, a relative positioning system 10 isillustrated. The system 10 includes a first vehicle 12 including aGPS-Bluetooth system 14, which will be discussed later, a second vehicle16 also including a GPS-Bluetooth system 18, and a set of satellites(here illustrated as a first 20, second 22 and third 24) communicatingwith the GPS-Bluetooth 14, 18 on board the vehicles 12, 16.GPS-Bluetooth improves GPS for vehicle navigation and other purposes aswell as vehicle safety, navigation, crash and pre-crash sensing.

[0031] In the present embodiment, a GPS is fused with Bluetooth radiosto form the GPS-Bluetooth 14 and to generate a robust proximity deviceusing typical vehicle equipment. GPS devices are packaged with Bluetoothradios which are capable of finding the distance between the twodevices, transmitting satellite range information and synchronizingdevices on multiple vehicles.

[0032] FIGS. 2A-D illustrate different scenarios in which theGPS-Bluetooth 14, 18 is useful. These scenarios will be discussed indetail later.

[0033] Referring now to FIGS. 1 and 3, a vehicle system 50 including aninter-vehicle relative positioning or GPS-Bluetooth system 14, inaccordance with an embodiment of the present invention, is illustrated.Relative positioning refers to the position of the first vehicle 12relative to the second vehicle 16. One skilled in the art will realizethe importance of relative positioning in pre-crash and crash avoidancesystems.

[0034] The system 50 includes a GPS antenna 54 electrically coupled to aGPS unit 68. The GPS unit 68 includes a Radio Frequency (RF) unit 56, aDigital Signal Processor 57, and a Central Processing Unit 58(controller). The RF unit 56 is electrically coupled to a Digital SignalProcessor 57, which is electrically coupled to the controller 58. Thecontroller 58 is also electrically coupled to a first Bluetooth radio 60(master) and a second Bluetooth radio 62 (slave) and to a vehiclenetwork 64, which generates a network signal. The vehicle network signalmay include vehicle proximity information relative to the first vehicle12, as will be understood by one skilled in the art.

[0035] The satellites 20, 22, 24 send radio signals to the GPS antenna54 so that the GPS can determine the distance to each satellite.

[0036] The GPS antenna 54 receives position signals from the satellites20, 22, 24 for the first vehicle 12 and the second vehicle 16 andgenerates therefrom an antenna GPS signal.

[0037] The RF unit 56 receives the antenna GPS signal and isolates theapplicable signals from the satellites and generates GPS signals inresponse thereto. The Digital Signal Processor 57 receives the GPSsignals and takes the real-time, high-speed GPS signals and manipulatesthem to generate positioning data, as will be understood by one skilledin the art.

[0038] The controller 58 is preferably microprocessor-based such as acentral processing unit coupled to memory (RAM and/or ROM) andassociated input and output buses. The controller 58 can stand alone orbe part of another controller such as an Engine Control Unit or aPowertrain Control Module.

[0039] The controller 58 combines vehicle information received from theGPS antenna 54 and the vehicle network 64. The global positioning system68 receives timing and vehicle data via the GPS antenna 54 and generatesa global positioning signal, through the RF unit 56 and the digitalsignal processor 57, that is utilized by the controller 58 forgenerating a GPS-Bluetooth relative position signal.

[0040] The controller 58 controls routing of various information betweenvehicle electronic devices including through the GPS-Bluetooth relativeposition signal. Responsive vehicle devices include the first Bluetoothdevice 60, the global positioning system 68, and other possible vehiclecomponents not shown such as: a navigation system, object detectionsensors, countermeasure systems, or other vehicle electronic devices andcomponents.

[0041] Time domain of the controller 58 is divided into periods, in eachperiod at least one specific function is performed. Vehicles utilizingthe GPS-Bluetooth 14, which are in close proximity with each other, aresynchronized dynamically in order to perform the specific functions inan appropriate sequential order. The specific functions may include:inquiry and discovery of vehicle related data, transmitting andreceiving data to and from a vehicle forward of or behind the firstvehicle 12, or transmitting and receiving data to vehicles that are tothe left or to the right of the first vehicle 12. The time domain may besynchronized through the use of the GPS system 68, or by other methodsknown in the art.

[0042] System-on-chip designs are alternately included therebyelectrically coupling the GPS unit 68, the controller 58 and theBluetooth radios 60, 62 on a single chip.

[0043] Normal GPS positioning can be augmented by using GPS devicesfitted with Bluetooth radios that communicate with the vehicles withinan area through a single piconet.

[0044] A piconet is a collection of devices connected via Bluetoothtechnology in an ad hoc fashion. A piconet starts with two connecteddevices, such as a portable PC and cellular phone, and may grow to eightconnected devices. All Bluetooth devices are peer units and haveidentical implementations. When establishing a piconet, however, oneunit (in the present embodiment, the first Bluetooth radio 60) will actas a master and the other(s) Bluetooth radio(s) as slave(s) for theduration of the piconet connection. All devices have the same physicalchannel defined by the master device parameters. A piconet is alsoformed when the first Bluetooth radio 60 is on the first vehicle 12 anda second Bluetooth radio 62 is on the second vehicle 16.

[0045] The present invention is embodied with two Bluetooth radios 60,62 wherein the first Bluetooth radio 60 generates discovery services andthe second Bluetooth radio 62 generates range and synchronization. TheBluetooth radios 60, 62 are tightly coupled to the GPS unit 68 soBluetooth can synchronize a system clock and transfer informationrapidly. The Bluetooth radios 60, 62 must be equipped for range finding,synchronization and Doppler velocity measurements. The GPS-Bluetooth 14can be either battery powered or externally powered.

[0046] The first Bluetooth radio 60 communicates with otherGPS-Bluetooth on other vehicles and the second Bluetooth radio 62communicates with ancillary devices. Important to note is that alternateembodiments include only one Bluetooth radio per vehicle. The presentinvention includes a GPS-Bluetooth Frequency Hopping Spread Spectrum(FHSS) methodology for communication between the GPS 68 and Bluetoothunits 60, 62.

[0047] The GPS-Bluetooth 14 is adapted for use with cars, trucks, boats,busses, bicycles, pedestrians and almost any vehicle that requiresproximity measurements to vehicles or objects in the vicinity. TheGPS-Bluetooth 14 can also be placed at stationary locations, such asintersections, docks, shopping malls, urban canyons, etc. to supplementnormal GPS.

[0048] In one embodiment, a first Bluetooth radio 60 is attached to aGPS 68 to transfer data to other Bluetooth radios (e.g. a secondBluetooth radio 62) attached to the GPS 68 to support Differential GPSand interferometric, methods such as Carrier-Phase Differential GPS.

[0049] GPS on multiple vehicles connected by Bluetooth radios shareephemeris information, speeding the cold start process for GPSreceivers. If a GPS unit does not have current information on thelocation of the satellites 20, 22, 24 it normally takes 12.5 to 25minutes to download the complete set from the satellites. A receiverequipped with Bluetooth connects with a similarly equipped receiver thathas current ephemeris data and downloads it immediately.

[0050] Time synchronization is achieved for a group of GPS receiverswith Bluetooth radios if two or more radios are used on each GPSreceiver. In this way each radio can have a direct connection to morethan one neighbor creating a mesh topology network on which thesynchronization is performed.

[0051] Time synchronization is also achieved for a group of GPSreceivers with Bluetooth radios when each GPS receiver has only oneBluetooth radio. In this case synchronization is achieved using apiconet or scatternet Bluetooth configuration between two vehicles.

[0052] The range, velocity measurement, and time synchronizationpossible with the Bluetooth protocol allow a reduction in the number ofsatellites or pseudolites that must be visible to a group of GPSreceivers. These benefits also increase the accuracy of the PVTmeasurements.

[0053] The aforementioned system components can be packaged into aself-contained package and can be installed in new vehicles or as aretrofit into vehicles not so equipped. The GPS-Bluetooth 14 uses atleast one Bluetooth radio to communicate with other devices in thevehicle 12 such as the navigation system, a Telematics computer andsafety devices as required.

[0054] The vehicle network 64 may be an internal or external vehiclenetwork. The controller 58 may be electrically coupled to the vehiclenetwork 64 via a personal computer memory card international association(PCMCIA) port, a Cardbus, a miniature card, an instrumentation, systems,and automation society (ISA) bus, a peripheral component interface (PCI)bus, or other port, bus, or card known in the art. The vehicle network64 may contain a central computer or storage center for vehicle networkinformation contained within the network signals.

[0055] Rather than including two GPS units in the first vehicle 12 tocompute position, velocity and time (PVT) information, and transmittingit between the vehicles 12, 16, one embodiment includes a Bluetoothconnection established between the GPS 68 on the first vehicle 12(vehicle a) and the GPS on the second vehicle 16 (vehicle b). Thisconnection is designed to compute the range velocity from the Dopplereffect and to synchronize the two units. This is achieved within thefirst vehicle 12 central processing unit through the following equations(in view of FIG. 1):

[0056] The position of vehicles a and b (first and second vehicles 12,14) can be computed by solving the following system of equations:

P _(a,b)={square root}{square root over ((x _(a) −x _(b))²+(y _(a) −y_(b))²+(z _(a) −z _(b))²)},

[0057] where

[0058] P_(a,b)=Measured range between vehicles 12, 16 through Bluetoothranging, as illustrated in FIG. 1.

P _(a) ^(J)={square root}{square root over ((x _(a) −x _(J))²+(y _(a) −y_(J))²+(z _(a) −z _(J))²)}+ct; for J=1 . . . N; N<2.

P _(b) ^(J)={square root}{square root over ((x _(b) −x _(J))²+(y _(b) −y_(J))²+(z _(b) −z _(J))²)}+ct; for J=1 . . . N; N<2.

[0059] Where P_(a) ^(J)=Range (distance) between the vehicle a and thesatellite J. Range is computed by “time of flight” and velocity (rate ofchange in range) by Doppler shift.

[0060] And X_(N)=X coordinate of object N in Earth Centered Coordinates.Y_(N)=Y coordinate of object N in Earth Centered Coordinates. Z_(N)=Zcoordinate of object N in Earth Centered Coordinates. N=a,b,c,d . . .for car a,b,c,d . . . or 1,2,3 for satellites 1,2,3. Only thosesatelites that are visible will be included in the list of J satellites.

[0061] P_(b) ^(J)=Distance between the satellite J and the vehicle b,P_(a,b)=Distance between Vehicle a and b determined by Bluetooth rangefinding, {x_(a),y_(a),z_(a)}=Position of vehicle a,{x_(b),y_(b),z_(b)}=Position of Vehicle b, and t=Time difference betweenthe synchronized GPS receivers and the satellite 20.

[0062] The system of equations for velocity is identical to that ofposition, except the ranges between vehicles is replaced by the rate ofchange in range. Rate of change is typically determined using Dopplershifts rather than time of flight for the range calculation. That is:

{dot over (P)} _(a) ^(J)={square root}{square root over ((x)} _(a) −{dotover (x)} _(J))²+({dot over (y)} _(a) −{dot over (y)} _(J))²+({dot over(z)} _(a) −{dot over (z)} _(J))²+c{dot over (t)}; for J=1 . . . N; N<2.

[0063] Where {dot over (P)}_(a) ^(J)=Time rate of change in distancebetween the satellite J (e.g. any one of satellites 20, 22, 24) and thevehicle a (first vehicle 12).

{dot over (P)} _(a) ^(J)={square root}{square root over ((x)} _(a) −{dotover (x)} _(J))²+({dot over (y)} _(a) −{dot over (y)} _(J))²+({dot over(z)} _(a) −{dot over (z)} _(J))²+c{dot over (t)}; for J=1 . . . N; N<2.

[0064] Where {dot over (P)}_(b) ^(J)=Time rate of change in distancebetween the satellite J and the vehicle B (second vehicle 16).

{dot over (P)} _(a,b)={square root}{square root over ((x)} _(a) −{dotover (x)} _(b))²+({dot over (y)} _(a) −{dot over (y)} _(b))²+({dot over(z)} _(a) −{dot over (z)} _(b))².

[0065] Where {dot over (P)}_(a,b)=Time rate of change in distancebetween vehicle a and b determined by Bluetooth range finding. And {{dotover (x)}_(J),{dot over (y)}_(J),{dot over (z)}_(J)}=Velocity ofsatellite J. Unknowns include {{dot over (x)}_(a),{dot over(y)}_(a),{dot over (z)}_(a)}=Velocity of vehicle a, {{dot over(x)}_(b),{dot over (y)}_(b),{dot over (z)}_(b)}=Velocity of vehicle b,and {dot over (t)}=Time rate of change in the time difference betweenthe synchronized GPS receivers and the satellite system.

[0066] Important to note is that alternate forms of the aforementionedequations are also included in the present invention. In other words, inthe case of two vehicles a, b where a sees satellites 3, 6 and 8 and bsees satellites 1, 6 and 8, the system of equations follows in whichthere are seven equations and seven unknowns (X_(a), Y_(a), Z_(a),X_(b), Y_(b), Z_(b), t):

P_(a,b)={square root}{square root over ((X _(a) −X _(b))²+(Y _(a) −Y_(b))²+(Z _(a) −Z _(b))²)} Range (distance) from car “a” to car “b.”

P_(a) ³={square root}{square root over ((X _(a) −X ₃)²+(Y _(a) −Y ₃)²+(Z_(a) −Z ₃₎ ²)}+ct Range (distance) from car “a” to Satelite “3.”

P_(a) ⁶={square root}{square root over ((X _(a) −X ₆)²+(Y _(a) −Y ₆)²+(Z_(a) −Z ₆₎ ²)}+ct Range (distance) from car “a” to Satelite “6.”

P_(a) ⁸={square root}{square root over ((X _(a) −X ₈)²+(Y _(a) −Y ₈)²+(Z_(a) −Z ₈₎ ²)}+ct Range (distance) from car “a” to Satelite “8.”

P_(b) ¹={square root}{square root over ((X _(b) −X ₁)²+(Y _(b) −Y ₁)²+(Z_(b) −Z ₁₎ ²)}+ct Range (distance) from car “b” to Satelite “1.”

P_(b) ⁶={square root}{square root over ((X _(b) −X ₆)²+(Y _(b) −Y ₆)²+(Z_(b) −Z ₆₎ ²)}+ct Range (distance) from car “b” to Satelite “6.”

P_(b) ⁸={square root}{square root over ((X _(b) −X ₈)²+(Y _(b) −Y ₈)²+(Z_(b) −Z ₈₎ ²)}+ct Range (distance) from car “b” to Satelite “8.”

[0067] More generally, the system of equations for many cars a,b,c,d . .. and many satellites 1,2,3,4 . . . Can be stated as:

P _(m,n)={square root}{square root over ((X _(m) −X _(n))²+(Y _(m) Y_(n))²+(Z _(m) −Z _(n))²)}

[0068] where P_(m,n) is a list of equations for each vehicle m=a,b,c,d .. . and vehicle n=a,b,c,d . . . such that m ≠n and P_(m,n) is known.P_(m) ^(J) ^(_(m)) ={square root}{square root over((X_(a)−X₃)²+(Y_(a)−Y₃)²+(Z_(a)−Z₃)²)}+ct where P_(m,J) is a list ofequations for each vehicle m=a,b,c,d . . . and each satellite J_(m) forwhich range and position information is known.

[0069] Navigation data, vehicle speed data, accelerometer data, etc. canbe used to augment the solution to the aforementioned equations both forimproved accuracy and for temporary satellite disappearance situations.

[0070] The solution to the aforementioned system of equations isaccomplished through a direct solution, iterative solution, or Kahlmanfilter.

[0071] To locate each vehicle requires at least one equation for eachunknown. The number of unknowns is:

U=3N _(v)+1.

[0072] Where: N_(v)=number of vehicles.

[0073] The number of equations is determined by:

N _(e) =N _(m,n) +N ^(J) _(m).

[0074] Where: N_(m,n) number of known ranges between vehicles fromBluetooth. N^(J) _(m)=number of known ranges between satellites andvehicles. The value of N_(m,n) depends on the topography of the networkbetween the vehicles. With a typical Bluetooth piconet or the networkdepicted in FIG. 4, the range is known between the master and each ofthe slaves, or: N_(m,n)=N_(v)−1. Other network topologies could have adifferent relationship between the number of vehicles and the number ofknown ranges between the vehicles.

[0075] Referring again to FIGS. 2A-2D, several collision scenarios areillustrated in which GPS-Bluetooth can be applied for collisionavoidance. These include merging/lane change 70 of vehicles a and b,road intersection 72 of a and b, approaching head-on 74 of a and b, andfollowing 76 of a by b. FIG. 2A illustrated is a possible collision bytwo merging vehicles a,b. FIG. 2B illustrates a vehicle collision at anintersection. FIG. 2C illustrates a vehicle a passing a slower vehicle cand moving to a head-on collision with vehicle b. FIG. 2D illustratesvehicle a decelerating behind a stopped vehicle b while vehicle c isapproaching in the opposite lane.

[0076] If the aforementioned equations indicate a collision will occurin a short time, the damage of the collision can be mitigated bydeploying collision devices in advance of the collision. Further, over alonger time period, if a collision is possible, corrective measures maybe taken in response to the shared and synchronized Bluetooth signals.

[0077]FIG. 4 illustrates the use of GPS-Bluetooth to support a system 78for platooning vehicles. When vehicles platoon they move into groups oftightly spaced vehicles. This improves vehicle aerodynamics for fueleconomy and creates open spaces in the traffic flow for congestioncontrol. To successfully platoon, vehicles must implement controlalgorithms that use position, velocity and other parameters to controlthe speed of each vehicle. Illustrated are several vehicles (a, b, c, d,e) with Bluetooth links between vehicles in the platoon that are bothahead and behind (except for the vehicles in the front 80 and back 82 ofthe platoon 85). In another embodiment the GPS-Bluetooth may beconnected in a Bluetooth piconet.

[0078] In one embodiment, at least one satellite-GPS link is requiredper vehicle in the middle 84, two for the front and rear vehicles (e anda), and an additional one is required for timing. For a second case, twosatellites-GPS links per middle vehicle 84 are required, three for thefront and rear vehicles (e and a) and one more somewhere in the platoon85. Other information and assumptions can be made in a platoon tofurther reduce the number of satellite-GPS links and/or accuracyimprovements by using other information such as navigational data,velocity and acceleration data that may already be available on thevehicle. For example, the fact that the vehicles (a, b, c, d, e) travelon the earth can reduce the dependency on satellite information.

[0079] GPS-Bluetooth generates the necessary information for a humanoperator or a control system to join a number of vehicles in aformation. A common formation is the platoon 85, which is used to reducetotal wind drag on a group of vehicles (a, b, c, d, e) and to providebreaks in traffic for congestion control.

[0080] The combination of Bluetooth and global positioning systems inmultiple vehicles allows for more effective arbitration of communicationbetween vehicles. For example, instead of using request to send andclear to send commands and various handshaking protocols, synchronizedcommunication between the vehicles may occur. In a first time interval,messages may be transmitted in a forward direction from vehicle a tovehicle b, followed by vehicle b transmitting messages to vehicle c,followed by vehicle c transmitting messages to vehicle d, and finallyvehicle d transmitting messages to vehicle e. In a second time interval,messages may be transmitted in a rearward direction, from vehicle e tovehicle d, from vehicle d to vehicle c, from vehicle c to vehicle b, andfinally from vehicle b to vehicle a. By synchronizing transceivers inmultiple vehicles by a global clock signal from the global positioningunits, pattern signals may be altered in unison, reducing interferencebetween transceivers in close proximity.

[0081] Referring now to FIG. 5, a logic flow diagram 98 illustrating amethod relative positioning, in accordance with an embodiment of thepresent invention, is illustrated.

[0082] Logic begins in operation block 100 where the GPS antennareceives a vehicle signal from a vehicle in close proximity to the firstvehicle or from a stationary point. The vehicle signal may be in theform of a vehicle-to-vehicle communication signal. The vehicle signalmay include vehicle information relative to the first vehicle such asvehicle traveling velocity, vehicle distance, vehicle location, or othervehicle information known in the art. The vehicle information maypertain to the first vehicle or one or more vehicles in close proximityto the first vehicle.

[0083] In operation block 102, the Bluetooth connection is establishedbetween two GPS. The GPS are located on at least two vehicles, a vehicleand a stationary object, or a platoon of vehicles.

[0084] In operation block 104, the Bluetooth connection is used to shareinformation between the two GPS. Range and velocity are computed fromthe Doppler effect.

[0085] In operation block 106, the two GPS units are synchronizedEquations to compute location, range and velocity were discussedregarding FIG. 1. Other forms of the equations are also included in thepresent invention. For example, navigation data, vehicle speed data andaccelerometer data can be used to improve accuracy of calculations usingthe above equations.

[0086] The GPS-Bluetooth Frequency Hopping Spread Spectrum (FHSS)methodology can be adapted to other communications protocols that cansynchronize and be used for range measurements. Some of these protocolsare Orthogonal Frequency Division Multiplexing (OFDM), Ultra-widebandwidth (UWB) communications, and Direct-Sequence Spread Spectrum.

[0087] The above-described operation blocks are meant to be anillustrative example, the operation blocks may be performedsynchronously or in a different order depending upon the application.

[0088] Also throughout the above-described operation blocks, thecontroller or the vehicle network may be continuously collecting andsorting incoming vehicle related data contained within signals, such asthe GPS signal, the synchronization signal from the Bluetooth radios,the network signal, or other vehicle related signals. The vehiclerelated data may be stored and partitioned for the various specificfunctions, mentioned above.

[0089] In operation, the Bluetooth devices communicate satellite rangeand ephemeris data by normal Bluetooth communication. This makes itpossible to use the Bluetooth radio connections to reduce the number ofsatellites required to be visible to the GPS while improving theaccuracy of the measurements.

[0090] The method of the present invention for communicating betweenvehicles having GPS-Bluetooth devices includes receiving timing andvehicle data, generating a GPS signal, computing range and velocitythrough Doppler shift, sharing information between the Bluetoothdevices, and synchronizing the GPS-Bluetooth devices.

[0091] The present invention incorporates the advantages associated withBluetooth and global positioning systems with commonly used vehicleelectronic devices and additional control logic into a singleinter-vehicle wireless communication and warning system. The presentinvention is self-supporting, has quick communication capability betweenvehicles, and has no single point of failure allowing safety relateddata to be reliably and quickly communicated. The present invention alsoprovides quick switching, direct communication, and minimum interferenceof pattern signals.

[0092] Using this method fewer satellites need to be visible to each GPSunit to get a position and velocity solution. If additional satellitesare visible these can be used to improve the accuracy of the solution.Most importantly for pre-crash sensing the distance between the vehiclesis known very precisely, so the time to impact can be accuratelycomputed.

[0093] The above-described apparatus and method, to one skilled in theart, is capable of being adapted for various purposes and is not limitedto the following systems: automotive vehicle systems, control systems,communication systems, or other systems that may utilize a smart antennaor the like. The above-described invention may also be varied withoutdeviating from the spirit and scope of the invention as contemplated bythe following claims.

What is claimed is:
 1. A relative vehicle positioning system for a firstvehicle comprising: a GPS antenna adapted to receive satellite signalsgenerated in response to relative vehicle positioning and generatetherefrom a GPS signal; a first Bluetooth radio adapted to exchangebearing information with a second vehicle and generate therefrom a PVTsignal; and a GPS unit comprising a controller adapted to receive saidGPS signal and said PVT signal and generate therefrom, a GPS-Bluetoothrelative position signal.
 2. The system of claim 1 further comprising asecond Bluetooth radio coupled to the first vehicle and adapted tosynchronize the first vehicle with said second vehicle.
 3. The system ofclaim 2 wherein said second Bluetooth radio is adapted to transfer datato other Bluetooth radios attached to said GPS unit to supportDifferential GPS and interferometric methods.
 4. The system of claim 2wherein said second Bluetooth radio and a third Bluetooth radio on saidsecond vehicle generate a mesh topology network on which saidsynchronization is performed.
 5. The system of claim 1 wherein a timesynchronization is generated between said first Bluetooth radio and asecond Bluetooth radio on said second vehicle through a piconetBluetooth configuration.
 6. The system of claim 1 wherein saidGPS-Bluetooth generates a platoon signal whereby a human operator or acontrol system receive said platoon signal and control a number ofvehicles in a formation in response thereto.
 8. The system of claim 1wherein said GPS-Bluetooth is either battery powered or externallypowered.
 9. The system of claim 1 wherein a second GPS-Bluetooth iscoupled to a stationary location.
 10. The system of claim 1 wherein saidGPS-Bluetooth is adapted to use communication protocols that cansynchronize and be used for range measurements.
 11. A relative vehiclepositioning system for a first vehicle comprising: a GPS antenna adaptedto receive satellite signals generated in response to a relative vehiclepositioning and generate therefrom a GPS signal; a first Bluetooth radioadapted to exchange bearing information with a second vehicle andgenerate therefrom a PVT signal; a second Bluetooth radio coupled to thefirst vehicle adapted to synchronize the first vehicle with said secondvehicle; a vehicle network adapted to generate a network signal; and aGPS unit comprising a controller adapted to receive said GPS signal,said PVT signal and said network signal,and generate therefrom, aGPS-Bluetooth relative position signal.
 12. The system of claim 11wherein said second Bluetooth radio is adapted to transfer data to otherBluetooth radios attached to said GPS unit to support Differential GPSand interferometric methods.
 13. The system of claim 11 wherein saidsecond Bluetooth radio and a third Bluetooth radio on said secondvehicle generate a mesh topology network on which said synchronizationis performed.
 14. The system of claim 11 wherein said GPS-Bluetooth iseither battery powered or externally powered.
 15. A method ofcommunicating between vehicles having GPS-Bluetooth devices comprising:receiving timing and vehicle data; generating a GPS signal; computingrange through time of flight and velocity through Doppler shift; sharinginformation between the Bluetooth devices; and synchronizing theGPS-Bluetooth devices.
 16. The method of claim 15 wherein sharingfurther comprises sharing ephemeris information.
 17. The method of claim15 wherein synchronizing further comprises synchronizing a piconetBluetooth configuration.
 18. The method of claim 15 further comprisinggenerating a platoon signal whereby a human operator or a control systemreceive said platoon signal and control a number of vehicles in aformation in response thereto.
 19. The method of claim 15 furthercomprising activating a vehicle system in response to said positionsignal, wherein said vehicle system comprises a pre-crash system, awarning system, a navigation system, an avoidance system or a safetysystem.